 /*******************************************************************************
  * Copyright (c) 2004, 2005 IBM Corporation and others.
  * All rights reserved. This program and the accompanying materials
  * are made available under the terms of the Eclipse Public License v1.0
  * which accompanies this distribution, and is available at
  * http://www.eclipse.org/legal/epl-v10.html
  *
  * Contributors:
  * IBM Corporation - initial API and implementation
  *******************************************************************************/
 package org.eclipse.core.internal.content;

 import java.io.*;
 import org.eclipse.core.runtime.QualifiedName;
 import org.eclipse.core.runtime.content.IContentDescription;
 import org.eclipse.core.runtime.content.ITextContentDescriber;

 /**
  * This class provides internal basis for text-based content describers.
  *
  * <p>
  * Note: do not add protected/public members to this class if you don't intend to
  * make them public API.
  * </p>
  *
  * @see org.eclipse.core.runtime.content.XMLRootElementContentDescriber
  * @since 3.0
  */
 public class TextContentDescriber implements ITextContentDescriber {

     private final static QualifiedName[] SUPPORTED_OPTIONS = {IContentDescription.BYTE_ORDER_MARK};

     /*
      * (non-Javadoc)
      * @see org.eclipse.core.runtime.content.ITextContentDescriber#describe(java.io.Reader, org.eclipse.core.runtime.content.IContentDescription)
      */
     public int describe(Reader contents, IContentDescription description) throws IOException {
         // we want to be pretty loose on detecting the text content type
 return INDETERMINATE;
     }

     /*
      * (non-Javadoc)
      * @see org.eclipse.core.runtime.content.IContentDescriber#describe(java.io.InputStream, org.eclipse.core.runtime.content.IContentDescription)
      */
     public int describe(InputStream contents, IContentDescription description) throws IOException {
         if (description == null || !description.isRequested(IContentDescription.BYTE_ORDER_MARK))
             return INDETERMINATE;
         byte[] bom = getByteOrderMark(contents);
         if (bom != null)
             description.setProperty(IContentDescription.BYTE_ORDER_MARK, bom);
         // we want to be pretty loose on detecting the text content type
 return INDETERMINATE;
     }

     /*
      * (non-Javadoc)
      * @see org.eclipse.core.runtime.content.IContentDescriber#getSupportedOptions()
      */
     public QualifiedName[] getSupportedOptions() {
         return SUPPORTED_OPTIONS;
     }

     byte[] getByteOrderMark(InputStream input) throws IOException {
         int first = (input.read() & 0xFF);//converts unsigned byte to int
 int second = (input.read() & 0xFF);
         if (first == -1 || second == -1)
             return null;
         //look for the UTF-16 Byte Order Mark (BOM)
 if (first == 0xFE && second == 0xFF)
             return IContentDescription.BOM_UTF_16BE;
         if (first == 0xFF && second == 0xFE)
             return IContentDescription.BOM_UTF_16LE;
         int third = (input.read() & 0xFF);
         if (third == -1)
             return null;
         //look for the UTF-8 BOM
 if (first == 0xEF && second == 0xBB && third == 0xBF)
             return IContentDescription.BOM_UTF_8;
         return null;
     }

 }

